It's one thing to be lip synching along to your favorite songs in your Brooklin homes while nobody's watching or caring that your screwing up the lyrics but it's another thing when the actual musicians themselves lip synch. There is nothing cool or awesome about musicians lip synching and if you're old enough to remember the Milli Vanilli scandal then you know exactly what we're talking about.
We except a certain level of professionalism when it comes to musicians and that's especially true if you've paid your hard earned money that you saved up from your Canadian architect paychecks to attend a live concert of a band you love only to go to the concert and they lip synch throughout the entirety of the show. It's called a live concert event for a reason but some artists take the route of lip synching at their shows regardless. Some musicians defend lip synching at their concert because not singing live saves them from straining their voice while also allowing them to maximize their energy into other parts of the show such as dancing.
You don't see too many doctors, dental consultants, retail store managers, etc., claim showmanship in the name of the work responsibility but some musicians do so without a problem. Musicians that lip synch at concerts are taking a shortcut and underselling what their fans paid for. There's really no point in going to a concert if all the singer is going to do is mouth the words to their hits songs. If that's the case you could save yourself some money and spend it on family rules wall art instead and then just play their music at home while lip synching yourself.
There are moments where lip synching is a must by musicians and even if they can justify the reasons why they lip synch it doesn't make lip synching any less controversial. Some reasons why musicians lip synch include covering up for an illness, making up for live performance deficiencies, making up for a lack of rehearsal time, simplifying the sound mixing process, covering up for a lack of on-stage confidence, and eliminating any chance of bad notes being hit.
Not only do fans frown upon the practice of lip synching but so too do certain musicians who believe that lip synching is only used by less talented musicians and that if they were a true artist they would not have to resort to lip synching. That's a valid argument that many fans support. There's a difference hearing a song being sung live versus it being lip synched live and the latter doesn't always go well; it's kind of like renting beachfront rentals based on a picture and then showing up for your stay only to find out what you rented resembles more of an outhouse than a beautiful vacation property.